MINNEAPOLIS / ST. PAUL (Feb. 14, 2003) —Researchers at the University
of Minnesota have identified the protein responsible for disassembly of
donor nucleoli in the context of nuclear cloning. Although it was
already known that nucleoli, essential structures for protein
synthesis, normally disassemble or disappear for a period of time in
the early animal development and also during nuclear cloning, it was
not known until this study what causes this phenomenon. Researchers
hope the identification of the protein will lead to advances in cloning
techniques and potential therapies. The study will be published in the
journal Nature Cell Biology on Feb. 17.

“The nucleolus, one of the largest structures found within the cell’s
nucleus, contains numerous proteins that have essential roles in cell
biology, for cancer, stem cells, and aging,” said lead researcher
Nobuaki Kikyo, M.D, Ph.D., assistant professor of medicine, Stem Cell
Institute. “By understanding how the nucleolus disassembles and
reassembles, we hope to learn more about normal cell development, the
roles of specific proteins, and their impact on human diseases.”

In the cloning process, the genetic material is removed from an egg
cell, and then the nucleus containing the genetic material from a
somatic (or body-associated) cell is transplanted into the egg cell.
Kikyo and his team recreated the normal procedure by mixing somatic
cell nuclei and protein extract from frog eggs to purify the proteins
responsible for nucleolar disassembly. Kikyo identified the proteins,
FRGY2a and FRGY2b, that disassemble nucleoli without help of other
proteins. The nucleoli are later reassembled as they normally would be.

“The study shows that FRGY2 proteins may be able to transform adult
cells into something more like embryonic cells—young and actively
proliferating cells with flexibility to turn into many types of cells,”
said Kikyo. “Furthermore, this work shows that it is possible to
dissect the very mysterious process – cloning – with a biochemical
approach and identify key players in it.”